Year	Percent
1978-12-31	11.94
1979-12-31	17.095
1980-12-31	14.845
1981-12-31	15.405
1982-12-31	10.66
1983-12-31	9.315
1984-12-31	9.75
1985-12-31	11.69
1986-12-31	11.19
1987-12-31	8.595
1988-12-31	12.97
1989-12-31	15.06
1990-12-31	14.36
1991-12-31	10.895
1992-12-31	6.91
1993-12-31	5.36
1994-12-31	6.03
1995-12-31	6.485
1996-12-31	6.175
1997-12-31	7.47
1998-12-31	6.265
1999-12-31	5.2813
2000-12-31	5.7813
2001-12-31	4.0469
2002-12-31	3.97
2003-12-31	3.865
2004-12-31	4.795
2005-12-31	4.605
2006-12-31	5.22
2007-12-31	5.925
2008-12-31	2.15
2009-12-31	0.53
2010-12-31	0.615
2011-12-31	0.81
2012-12-31	0.47
2013-12-31	0.475
2014-12-31	0.465
2015-12-31	0.505
2016-12-31	0.3